This invention relates to navigation devices and more particularly to apparatus for providing improved underwater navigation capability to swimmer-divers, small submersibles, or the like.
Swimmer-diver navigation has been materially aided with the introduction of devices utilizing doppler effects of sonar to provide accurate data as to direction and speed of travel over the bottom. U.S. Pat. No. 3,810,080 to E. K. Hunter provides a good example of such a device which also incorporates for the diver's use a magnetic steering compass and a drift meter. The latter provides to the diver a visual indication of the amount of lateral drift he is experiencing, due to cross currents in the water.
While that device automatically gives the diver a quantitative drift indication, the amount of heading correction that he must effect to make his desired course good will require a mental computation that depends upon his skill and experience. In practice, making the necessary heading correction is made more difficult by the fact that each change in either heading or drift produces a resultant change in the other.
Moreover, it has been found that swimmer-divers using the navigation device of U.S. Pat. No. 3,810,080 experience difficulty in accurately reading the magnetic steering compass thereof while swimming and also watching the drift meter which is close to, but separate from the compass.
Accordingly, it is desirable to provide an underwater navigation device or system having a single, null type indicator that will tell the user whether he is actually heading in the proper direction to make good a predetermined desired course in spite of transverse currents and, if not, what steering correction he must effect to make the course good.